The present invention relates generally to video and graphics microdisplay systems, and more particularly to a system for the illumination of microdisplays.
The technology of using liquid crystal materials in microdisplays is relatively new. The liquid crystal material, which forms the optical component of the microdisplay, is placed directly on a silicon integrated circuit, or pixel array, under a transparent cover and the signals to turn the individual picture elements, or pixels, of the microdisplay on and off are generated on the silicon integrated circuit.
The term xe2x80x9cmicrodisplayxe2x80x9d is used since the display in a typical embodiment has an array of 1,024xc3x97768 pixels (the individual pixel size is approximately 12xcexc) and the silicon die is about 1.3 cmxc3x971 cm in area.
The microdisplay system works by having light from an ordinary light source pass through an illuminator, which converts non-polarized light from the ordinary light source into a polarized light beam. The polarized light beam is then directed onto the microdisplay. The microdisplay will reflect the light in a manner such that the plane of polarization of the light will or will not be rotated. The light then is reflected back to the illuminator which acts as an analyzer and causes the pixels to be bright or dark depending on whether the plane of polarization was rotated. The bright and dark pixels form a viewing image.
Applications for these microdisplays continue to expand. In one application, they are used for viewfinders for digital cameras and camcorders. In another, two microdisplays are fixed to a frame, such as eyeglasses, thereby giving a user a virtual image of a virtual computer screen, which is very lightweight and also very private.
Since microdisplays are small enough to be portable, batteries are used to provide power to illuminate the microdisplays. To minimize battery weight and maximize battery life, power consumption of the microdisplay must be minimized. High power consumption is one of the major problems with microdisplays. Attempts have been made in the art to use ambient light to illuminate microdisplays. However, the intensity of ambient light alone is generally insufficient to adequately illuminate microdisplays.
The present invention provides a micro display system that uses ambient light to illuminate the microdisplay. A wave-guide has a dye embedded therein which absorbs ambient light through the surfaces of the wave-guide and re-emits an augmented light, which is captured by the wave-guide. Total internal reflection in the wave-guide and reflection from a reflector at one end of the wave-guide direct substantially all the light through a light-transmissive end to an illuminator for illuminating the microdisplay. The microdisplay has a plurality of pixels which are activated to reflect light back through the illuminator for viewing the microdisplay image. This approach minimizes power usage and prolongs battery life that is particularly useful in portable microdisplay systems.
The present invention further provides a microdisplay system that uses ambient light to illuminate the microdisplay in color. A wave-guide has different dyes embedded in it which absorb ambient light and re-emit light in the three primary colors, namely red, green and blue. Total internal reflection in the wave-guide and reflection from a reflector at the end of the wave-guide direct the re-emitted light through the transmissive end into a solid-state color wheel. The solid-state color wheel is controlled by the integrated circuit to selectively permit the transmission of individual color lights to an illuminator for illuminating the microdisplay in synchronization with the activation of the pixels. The pixels are activated to reflect light back through the illuminator for viewing the microdisplay image.
The present invention further provides a microdisplay system that uses ambient light to illuminate the microdisplay in color. Three wave-guides have different dyes embedded in them which absorb ambient light and re-emit light in the three primary colors, namely red, green and blue. Total internal reflections in the wave-guide and reflections from reflectors at the ends of the wave-guides direct the re-emitted light through the transmissive ends into liquid crystal (LC) shutters. Each of the LC shutters is independently controlled to turn on or shut off the transmission of the respective color light through the respective LC shutters to a coupler which directs the light to an illuminator for illuminating the microdisplay. The microdisplay has a plurality of pixels which are activated to reflect light back through the illuminator for viewing the microdisplay image. This approach minimizes power usage and prolongs battery life that is particularly useful in portable microdisplay systems.
The present invention further provides a microdisplay system having an auxiliary, powered light source for use with the wave-guides for supplemental illumination of the microdisplay.
The above and additional advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.